Question: 6 glue sticks cost $10.50. Which equation would help determine the cost of 4 glue sticks?
Solution: There are several equations that could help determine the cost, each with a slightly different approach. We know the cost of 6 glue sticks. We want to know the cost of 4 glue sticks. We can write the numbers of glue sticks as a proportion: $\dfrac{6}{4}$ We know 6 glue sticks costs $10.50. We can let $x$ represent the unknown cost of 4 glue sticks. The proportion of these costs can be expressed as: $\dfrac{\$10.50}{x}$ The cost changes along with the number of glue sticks purchased, and so the two proportions are equivalent. $\dfrac{6}{4} = \dfrac{\$10.50}{x}$